SPARC: How to Set the Number of Volume Names and Disk Sets

With the Solaris 10 release, Solaris Volume Manager has been enhanced to configure volumes dynamically. You no longer need to edit the nmd and the md_nsets parameters in the /kernel/drv/md.conf file. New volumes are dynamically created, as needed.

This procedure describes how to determine the number of Solaris Volume Manager volume names and disk sets that you need for your configuration. This procedure also describes how to modify the /kernel/drv/md.conf file to
specify these numbers.

Tip –

The default number of volume names per disk set is 128, but many configurations need more than the default. Increase this number before you implement a configuration, to save administration time later.

At the same time, keep the value of the nmdfield and the md_nsets field as low as possible. Memory structures exist for all possible devices as
determined by nmdand md_nsets, even if you have not created those devices. For optimal performance, keep the value of nmd and md_nsets only slightly higher than the number of volumes that you plan
to use.

Before You Begin

Calculate the total number of disk sets that you expect to need in the cluster, then add one more disk set for private disk management.

The cluster can have a maximum of 32 disk sets, 31 disk sets for general use plus one disk set for private disk management.
The default number of disk sets is 4. You supply this value for the md_nsets field in Step 3.

Calculate the largest volume name that you expect to need for any disk set in the cluster.

Each disk set can have a maximum of 8192 volume names. You supply this value for the nmd field
in Step 3.

Determine the quantity of volume names that you expect to need for each disk set.

If you use local volumes, ensure that each local volume name on which a global-devices
file system, /global/.devices/node@ nodeid, is mounted is unique throughout the cluster and does not use the same name as any device-ID name in the cluster.

Tip –

Choose a range of numbers to use exclusively for device-ID names and a range for each node to use exclusively for its local volume names. For example, device-ID names might use the range from d1 to d100. Local volumes
on node 1 might use names in the range from d100 to d199. And local volumes on node 2 might use d200 to d299.

Calculate the highest of the volume names that you expect to use in any disk set.

The quantity of volume names to set is based on the volume name value rather
than on the actual quantity . For example, if your volume names range from d950 to d1000, Solaris Volume Manager software requires that you set the value at 1000 names, not 50.

On each node, become superuser and edit the /kernel/drv/md.conf file.

Caution –

All cluster nodes (or cluster pairs in the cluster-pair topology) must have identical /kernel/drv/md.conf files, regardless of the number of disk sets served by each node. Failure to follow this guideline can result in serious Solaris Volume Manager errors
and possible loss of data.